The invention relates to apparatus for testing lightning and surge arresters and, in particular, to portable apparatus for field testing of such arresters.
Lightning and surge arresters, hereinafter referred to as "lightning arresters," are designed to protect a power transmission or distribution system by shunting to ground high voltage surges, such as those caused by lightning. Arresters are subjected to stresses of very high voltages and currents and can be damaged by lightning and can deteriorate over time. Eventually, lightning arresters can fail, and when they do it is usually a violent failure, resulting in destruction of the arrester, as by explosion.
Arresters are often installed on an overhead or underground power transmission or distribution system while the system is live. Connecting a weak or damaged arrester to a live line can result in an immediate or eventual catastrophic failure. If the failure is immediate, the line personnel are endangered by the resulting system fault. If the failure is eventual, another outage is caused, peripheral equipment is damaged and the service crew must repair the damage and restore power.
Known lightning arrester testers are typically stationary, laboratory-based equipment, requiring highly skilled technical people to operate. While these laboratory systems provide sensitive tests that can find even very subtle types of arrester damage, they are expensive and inconvenient and do not permit the testing of arresters in the field.
It is also known to provide lightning arresters with built-in monitoring circuits to provide an indication when leakage currents reach an unacceptably high level. But this requires a specialized arrester design and is of no assistance in testing standard arresters without the built-in monitoring circuitry.